Refer to FIG. 1 for a conventional light-emitting diode (LED), wherein an N-type gallium nitride layer (n-GaN) 2, a multi-layer quantum well (MQW) 3, a P-type gallium nitride (p-GaN) 4 are sequentially epitaxially grown on a substrate 1; then a P-type metallic pad (p-Pad) 5 and an N-type metallic pad (n-Pad) 6 are coated on the abovementioned epitaxial layers. If the LED is to be used as a high-power and large-size LED, metallic mesh wires 7 and 8 are simultaneously coated on the epitaxial layers during coating the P-type metallic pad 5 and the N-type metallic pad 6. For a high-power and large-size LED, a high-reflectivity reflecting layer 9 is further coated on the grinded and polished substrate 1 to increase the brightness of the LED by reflection.
In a high-power and large-size LED, the P-type metallic pad 5, the N-type metallic pad 6 and the metallic mesh wires 7 and 8 are usually uniformly distributed on the light-emitting region and occupy a considerable area. The conventional P-type metallic pad 5, N-type metallic pad 6 and metallic mesh wires 7 and 8 are usually made of indium tin oxide (ITO), nickel/gold, or chromium/gold. However, ITO has a problem of peel-off and is likely to react with silver. When cooperating with silver, the nickel/gold or chromium/gold has a reflectivity of only 50-60%, absorbs a considerable amount of light, and results in an unneglectable light loss, which not only decreases the brightness of LED but also generates waste heat. Thus, the service life of LED is decreased by high temperature.